Thermodynamic Assessment of the Mg–La–Nd System

Abstract

Ternary Mg–La–Nd and constituent binary Mg–La and Mg–Nd systems were assessed after a critical review of the experimental data and ab initio data using the CALPHAD method. The enthalpies of formation of the end-member compounds of the Mg(La, Nd) and Mg₃(La, Nd) phases were obtained by ab initio calculations and then used to determine their model parameters. The binary Mg–La system was revised to maintain the consistency of the thermodynamic models, whereas the binary Mg–Nd system was reassessed to describe the homogeneity ranges of the hcp, dhcp, and Mg₃Nd phases. Moreover, the metastable Mg₁₂Nd phase was modeled to reproduce the phase constituents of the as-cast Mg–Nd alloys. Based on the updated binary descriptions, the ternary Mg–La–Nd system was assessed according to recent experimental data. Through a comprehensive comparison between the calculated and experimental phase equilibria and thermochemical property data, a reasonable agreement was achieved for the binary and ternary systems.